Method and apparatus for conditioning crop materials

ABSTRACT

As crop materials are severed from the field, they pass through two successive pairs of counter-rotating conditioning rolls before being returned to the ground. The front rolls are preferably ribbed, metal rolls wherein the ribs of one roll are intermeshed with those of the other roll so as to crimp the stems of the crop materials as they pass between the rolls. The hard metal ribs also aggressively feed the materials rearwardly into the second set of rolls, which are preferably compressive surface rolls made of rubber or the like and provided with wide, intermeshed bars about their periphery. The tension mechanism for the rolls includes single-acting hydraulic cylinders that squeeze the rolls together to the extent permitted by adjustable stop structure used to set gaps between the rolls. In typical operations, the gap between the rear rolls is set to be considerably smaller than the gap between the front rolls. Great flexibility in the degree of conditioning experienced by the crop materials is achieved by the nature of the rolls and the ease with which roll pressure and spacing can be adjusted.

TECHNICAL FIELD

This invention relates to the field of crop harvesting equipment and,more particularly, to a method and apparatus for obtaining conditionedcrop materials with improved drying characteristics by passing theharvested materials between successive sets of paired conditioningrolls.

BACKGROUND AND SUMMARY

It is known in the art to pass harvested materials, such as hay, throughmultiple sets of paired, oppositely rotating rolls in an effort tocondition, crush, and/or mascerate the stems of the crop materials. See,for example, U.S. Pat. No. 6,050,070 issued to Ivan J. Cook on Apr. 18,2000. See also a commercially available machine sold under the tradename and mark MACERATOR 6600 by AgLand Industries Inc. of Arborg,Manitoba Canada. However, for a variety of reasons, the prior artsystems have not been entirely satisfactory.

The present invention provides a novel method and apparatus forobtaining improved crop conditioning. It also provides greaterflexibility for the operator to choose the degree of conditioning towhich the crop materials will be subjected. In a preferred form of theinvention, two sets of paired, oppositely rotating rolls are used, withthe front pair comprising a pair of non-compressible, metal rolls havinglongitudinally extending helical ribs about their periphery to perform aconditioning and feeding action. The ribbed metal rolls feed theconditioned materials directly to a rear pair of counter-rotatingcompressible surface rolls having longitudinally extending, relativelywide helical bars about their periphery. Like the narrow ribs on thefront rolls, the wide bars on the rear rolls intermesh so as to providean aggressive conditioning action as the crop materials pass between therear rolls. Each set of rolls can be readily adjusted to control thetension force maintained on the rolls and the gap between the rolls.

The tension mechanism for the rolls includes a hydraulic circuit thatutilizes at least one hydraulic cylinder connected to a moveable roll ofeach pair. The circuit containing the cylinder may be pressurized up toa certain selected level and then maintained at such level by closing acontrol valve to trap fluid against escape to the reservoir. Preferably,a compressible gas accumulator is connected in parallel fluid flowrelationship with the cylinder to provide a yieldable, cushioningeffect. The tension on the front rolls can be adjusted separately fromthe tension on the rear rolls. The front and rear rolls are mounted insuch a way that the front rolls can move apart independently from therear rolls and vice versa.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a self-propelled harvester in thenature of a windrower incorporating the principles of the presentinvention;

FIG. 2 is an enlarged side elevational view of the header of thewindrower with end panel portions thereof removed to reveal details ofconstruction, the rolls being illustrated in their close togetherpositions;

FIG. 3 is a side elevational view of the header similar to FIG. 2 butwith additional structure removed to show the rolls in their closetogether positions of FIG. 2;

FIG. 4 is a side elevational view of the header similar to FIG. 2 butshowing the rolls in their fully open and spaced apart positions;

FIG. 5 is a side elevational view of the header similar to FIG. 3 butillustrating the rolls fully spaced apart corresponding to the conditionof things in FIG. 4;

FIG. 6 is an enlarged, fragmentary, rear, vertical cross-sectional viewtaken immediately behind the front rolls and looking forwardly to revealdetails of the mounting and drive arrangement for the front rolls;

FIG. 7 is an enlarged, fragmentary rear, vertical cross-sectional viewsimilar to FIG. 6 but taken further rearward than FIG. 6 from a pointimmediately behind the rear conditioning rolls and looking forwardly soas to reveal drive details for the rear rolls;

FIG. 8 is a fragmentary generally horizontal cross-sectional viewlooking downwardly through the two lower rolls illustrating theirmounting arrangement and their relationship to the center-gatheringaugers in front of the rolls; and

FIG. 9 is a schematic illustration of a simplified hydraulic circuit forapplying tensioning force to the rolls.

DETAILED DESCRIPTION

The present invention is susceptible of embodiment in many differentforms. While the drawings illustrate and the specification describescertain preferred embodiments of the invention, it is to be understoodthat such disclosure is by way of example only. There is no intent tolimit the principles of the present invention to the particulardisclosed embodiments. For example, the present invention has beenillustrated in connection with a self-propelled harvester. However, itwill be appreciated that the principles of the present invention are notlimited to use in a harvester, self-propelled or otherwise, and mayreadily be incorporated into a machine that does not severe cropmaterials from the field but only performs a separate conditioningfunction. Furthermore, while the harvester selected for purposes ofillustration is a sickle-type machine utilizing a reel and cross-augers,the principles of the present invention also have utility in harvestersutilizing rotary cutoffs with no reels or augers.

The self-propelled windrower 10 in FIG. 1 broadly includes a tractor 12and a header 14 mounted on the front end of tractor 12. Generallyspeaking, windrower 10 is capable of severing standing crop materialsfrom the ground as tractor 12 advances header 14 across the field,conditioning the stems of such materials as they are passed rearwardlythrough header 14, and then returning the conditioned materials to theground underneath tractor 12 in a windrow or swath depending upon theposition of various forming shields 16 shown in phantom in FIG. 1.Header 14 in the illustrated embodiment has a reciprocating sickle 18for severing standing materials from the ground, a rotating reel 20 forsweeping the standing materials into sickle 18 to improve cutoff, and apair of vertically spaced, oppositely rotating, full-length augers 22and 24 that converge the severed crop centrally and propel it rearwardlyas the machine advances. As shown particularly in FIGS. 6 and 7, header14 has a rear opening 26 behind augers 22, 24 for receiving cropmaterials therefrom and admitting such materials into the cropconditioning mechanism therebehind broadly denoted by the numeral 28.

In accordance with the present invention, the conditioning mechanism 28includes a pair of front, counter-rotating conditioning rolls 30 and 32and a pair of rear, counter-rotating, conditioning rolls 34 and 36.Front rolls 30, 32 have non-compressible surfaces made of a hardmaterial such as steel, while rear rolls 34, 36 have compressiblesurfaces and are made of softer materials such as rubber, neoprene orelastomer. In one preferred embodiment, rear rolls 34, 36 areconstructed from molded rubber layers that are cured and subsequentlymachined so as to provide a specially configured surface as explained inmore detail below, although the rear rolls may instead be provided withsmooth surfaces. Improved conditioning action can be obtained over afairly wide range of hardness of the compressible surface on rolls 34,36, but best results have been obtained using rubber having a hardnessof 70–80 durometer.

Front conditioning rolls 30, 32 may take the form of fluted or ribbedsteel rolls of the type used for many years in HESSTON brand windrowersand mower conditioners. Each of the front rolls 30, 32 thus has a seriesof radially outwardly projecting, somewhat triangular in cross sectionand relatively narrow ribs 38 that extend along the length of the rollin a helical pattern. Ribs 38 project outwardly from a cylindrical core40 of each roll and are spaced around the roll in such a manner that theribs on top roll 30 may intermesh with the ribs on bottom roll 32 duringoperation.

On the other hand, in the particular illustrated embodiment each of therear rolls 34, 36 is provided with a series of radially outwardlyprojecting, relatively wide bars 42 that are fewer in number and widerthan the ribs 38 on front rolls 30, 32. Bars 42 project outwardly from acylindrical core 44 on each rear roll and extend longitudinally the fulllength of the roll in a helical pattern. Preferably, the bars 42 ofupper and lower rear rolls 34, 36 are intermeshed with one another.

Front rolls 30, 32 are adapted for relative movement toward and awayfrom one another. Similarly, rear rolls 34, 36 are adapted for relativemovement toward and away from one another. In the illustratedembodiment, front rolls 30, 32 are mounted in such a way that lower roll32 can move toward and away from upper roll 30 to a limited extent,while the vertical position of upper roll 30 remains fixed. Thisrelationship could be reversed. On the other hand, upper rear roll 34 ismounted to move toward and away from lower rear roll 36 to a limitedextent while the position of lower rear roll 36 remains fixed. Thisrelationship could also be reversed. The details of constructionpermitting such mounting arrangement and movement are illustrated inparticular in FIGS. 2, 4 and 6–8, it being noted that only the left endsof the rolls are illustrated in several of those figures. Thus, thefollowing description will focus on the left end of the rolls, with theunderstanding that corresponding arrangements are provided at the rightends.

All of the rolls are provided with stub shafts projecting outwardly fromopposite ends thereof as exemplified by the stub shaft 44 of top frontroll 30. The stub shaft 44 of top front roll 30 is journaled by bearings46 that are in turn fixedly attached to an upright end wall 48 such thatthe axis of rotation of top front roll 30 does not move in anydirection. On the other hand, the stub shaft 50 of lower front roll 32passes through a generally upright slot 52 in end wall 48 and isjournaled by a set of bearings 54 that are attached to a supportassembly 56 swingable up and down about the axis of lower rear roll 34.Slot 52 is slightly arcuate with its center at the axis of the lowerrear roll 36. As illustrated in FIG. 8, the rear end of support assembly56 is pivotally mounted on a trunnion mount 58 that encircles the stubshaft 60 of lower rear roll 36 and is attached to a bearing 62 for stubshaft 60. Bearing 62, in turn, is fixedly secured to end wall 48 so asto remain in a fixed location at all times. The stub shaft 64 of upperrear roll 34 is journaled by a set of bearings (not shown) that are inturn carried by a vertically swingable support assembly 68 having itsaxis of swinging movement coinciding with the axis of top front roll 30.A trunnion mount 69 (FIG. 6) encircles stub shaft 44, pivotally supportsthe support assembly 68, and is fixed to bearing 46. Stub shaft 64 ofupper rear roll 34 passes through a generally upright slot 70 in endwall 48, such slot 70 being slightly arcuate with its center at the axisof rotation of upper front roll 30.

Tension is applied to the rolls 30–36 by four single-acting tensionhydraulic cylinders 72, 74, 76 and 78 as illustrated in FIG. 9. Tensioncylinders 72 and 74 are used for applying tension to the front rolls30–32, while the cylinders 76 and 78 are used for applying tension tothe rear rolls 34, 36. Front cylinders 72, 74 are located at oppositeends of lower front roll 32, while rear cylinders 76, 78 are located atopposite ends of upper rear roll 34. More specifically, each frontcylinder 72, 74 is secured to a corresponding end wall 48 along thelower front extremity thereof and projects upwardly therefrom forpivotal connection with the lower front extremity of support assembly56. Correspondingly, each rear cylinder 76, 78 is secured to the upperrear extremity of an end wall 48 and projects downwardly therefrom forpivotal connection with the upper rear extremity of support assembly 68.Cylinders 72–78 thus comprise part of a tension mechanism broadlydenoted by the numeral 80 in FIG. 9 that urges rolls 30, 32 and 34, 36relatively toward one another and resists their separation.

The front rolls 30, 32 are provided at their opposite ends withadjustable stop structure 82 for limiting movement of lower front roll32 upwardly toward upper front roll 30. As illustrated, for example, inFIGS. 2 and 4, such stop structure 82 includes an elongated member 84that passes through a hole (not shown) in an outturned flange 48 a ofthe lower edge of end wall 48 and connects at its upper end to the lowerfront extremity of support assembly 56. Adjacent its lower end, member84 is provided with a stop collar 86 that is adapted to abut the bottomside of outturned flange 48 a when lower front roll 32 is in its full upposition as illustrated in FIGS. 2 and 3. Preferably, the position ofstop collar 86 is adjustable such that, in a preferred embodiment, arunning gap can be established and adjusted between front rolls 30, 32.In one preferred embodiment, such adjustability is obtained byconstructing elongated member 84 in such a manner that there are tworelatively telescopic parts, namely an inner elongated shank 88 and anouter elongated sleeve 90 encircling inner shank 88. Outer sleeve 90 hasstop collar 86 fixed to the lower end thereof, while inner shank 88 ispivotally joined with support assembly 56 at an upper end and carries aset of adjusting nuts 92 at a lower, threaded end. Thus, adjusting theposition of nuts 92 on inner shank 88 changes the position of sleeve 90along the length of shank 88 to correspondingly place stop collar 86closer to or farther away from flange 48 a. In the opposite direction,to limit the extent of downward movement of lower front roll 32 awayfrom upper front roll 30, a stop bracket 94 is disposed to underlie andabut the lower edge of support assembly 56 as illustrated in FIG. 4, forexample. A similar stop structure 82 and stop bracket 94 are provided onthe right end of header 14.

Adjustable stop structure 96 is also provided for adjustably limitingthe movement of upper rear roll 34 in a downward direction toward lowerrear roll 36. As illustrated particularly in FIGS. 2 and 4, suchadjustable stop structure 96 is preferably identical to stop structure82. Like structure 82, stop structure 96 comprises an elongated member98 that is preferably constructed from a pair of relatively telescopingparts, i.e., an inner shank 100 and an outer sleeve 102 that is axiallyslidable along shank 100. The lower end of the shank 100 is pivotallyconnected to support assembly 68, while the upper end of shank 100 isthreaded to threadably receive a pair of adjustable nuts 104 that areadapted to bear against the outer face of a stop collar 106 on the upperend of sleeve 102. Member 98 passes through a hole 108 in an inturnedflange 48 b along the upper extremity of end wall 48, and stop collar106 is adapted to abut the upper extremity of a stop bracket 110 on endwall 48 when upper rear roll 34 is in its fully lowered position asillustrated, for example, in FIG. 2. In order to limit movement of upperrear roll 34 away from lower rear roll 36, a stop bracket 112 similar tostop bracket 94 is disposed above support assembly 68 for engagementwith the upper extremity of assembly 68 when upper rear roll 34 israised to its full extent and away from lower rear roll 36. Both ends ofupper rear roll 34 are provided with stop structures 96 and with stopbrackets 112.

As illustrated in FIG. 6, in one preferred embodiment the rolls 30, 32and 34, 36 are hydraulically driven via a hydraulic motor 114 having anoutput shaft 116. Output shaft 116 is connected via a U-joint drive lineto an input shaft 120 of a gear case 122. An output shaft 124 of gearcase 122 supplies driving power to upper front roll 30 via a telescopingU-joint drive line 126 coupled with stub shaft 44, and a gear box 128operably coupled with gear case 122 has an output 130 that suppliesdriving power to the lower front conditioning roll 32 via a telescopingU-joint drive line 132 operably coupled with stub shaft 50 of lowerconditioning roll 32. Gear box 128 is preferably a right angle box thatalso supplies driving power to other components of header 14 such as,for example, the sickle 18, which may be a double sickle such thatgearbox 128 would supply driving power only to the left half of thedouble sickle 18. A second right angle gear box (not shown) may beconnected to the stub shaft on the opposite end of lower front roll 32for the purpose of supplying driving power to the right end of suchdouble sickle.

As shown in FIG. 7 in addition to FIG. 6, gear case 122 also is providedwith an output shaft 134 that supplies driving power to the upper rearroll 34 via a telescoping U-joint drive line 136 operably coupled withstub shaft 64 of upper rear roll 34. Another output shaft 138 suppliesdriving power to lower rear roll 36 via a telescoping U-joint drive line140 operably coupled with stub shaft 60 of lower rear roll 36.

As noted earlier, tension cylinders 72–78 comprise part of a tensionmechanism broadly denoted by the numeral 80 and illustratedschematically in FIG. 9. In addition to the cylinders 72–78, tensionmechanism 80 also includes a reservoir 142 that supplies hydraulic fluidto the rest of the system via a pump 144. Pump 144 is located in asupply line 146 leading from reservoir 142 and controlled by asolenoid-operated, two-position valve 148. A return line 150 toreservoir 142 is controlled by a two-position, solenoid-operated controlvalve 152. A three position switch 154, which may be convenientlylocated on header 14 itself or in the operating cab of tractor 12, maybe used to energize solenoid valves 148 and 152. In the neutral positionas shown, switch 154 maintains valves 148 and 152 in their closedpositions such that no fluid may flow from pump 148 to the rest of thecircuit, and no fluid may flow out of the circuit back to reservoir 142.However, when switch 154 is engaged with contact 156, solenoid valve 148is actuated to allow the rest of the circuit to be charged withpressurized fluid. When switch 154 is moved into engagement with contact158, solenoid valve 152 is actuated to allow the rest of the circuit todrain to reservoir 142. Switch 154 may be located either in the tractorcab or on header 14.

A main line 160 is teed into the supply line 146 and return line 150between control valves 148 and 152. Main line 160 in turn branches intoa front tension line 162 and a rear tension line 164. Front tensioncylinders 72 and 74 are connected to front tension line 162 in parallelrelation to one another so that both cylinders 72 and 74 receivepressurized oil simultaneously and discharge pressurized soilsimultaneously. A suitable gas pressure accumulator 166, which may takethe form of a number of readily commercially available units, isconnected in parallel fluid flow communication with the two cylinders 72and 74 for cushioning the conditioning tension branch of the circuit. Anormally closed shut-off valve 168 is located in conditioning tensionline 162 ahead of cylinders 72 and 74, along with a pressure-indicatingmeter 170 so that oil may be trapped within cylinders 72, 74 when valve166 is closed. When valve 166 is open, cylinders 72, 74 may either becharged with oil or may discharge oil to reservoir 142, depending uponthe position of solenoid valves 148 and 152. Valve 168 and meter 170 maybe located either in the tractor cab or on the header 14.

Similarly, the rear tension line 164 has a compressive gas accumulator172 connected thereto between rear tension cylinders 76 and 78 so as tocushion that part of the circuit. A normally closed shut-off valve 174is located in line 164 above cylinders 76, 78, and a pressure indicatingmeter 176 is located in line 164 between valve 174 and the cylinders 76,78. When valve 174 is closed, fluid is trapped in rear tension cylinders76, 78, while when valve 174 is open, cylinders 76, 78 may either becharged with pressurized oil or may discharge oil to reservoir 142,depending upon the positions of the solenoid-powered control valves 148and 152. Valve 174 and meter 176 may be located either in the tractorcab or on the header 14.

OPERATION

Different crop conditions may call for different pressure settings onthe rolls as well as different gaps, if any, between the rolls.Moreover, there may be times when the operator simply wishes to changethe degree or severity of conditioning of the crop materials. Thepresent invention affords great flexibility in this respect.

Usually, but not necessarily, a gap is desired between front rolls 30,32, and such gap may be somewhat larger than in conventionalconditioning situations that use fluted steel rolls. The gap is measuredbetween the outermost tip of one of the ribs 38 and the cylindrical core40 of the opposing roll. Good results have been obtained where the gapis set in the range of 0.250 to 0.750 inches. Of course, the size of thegap during operations may temporarily increase significantly as slugs ofmaterial are passed therethrough and the lower roll 32 swings away fromthe upper roll 30. Preferably, the front rolls 30 and 32 do not touchone another.

Preferably, but not necessarily, the rear rolls 34, 36 are set to have aslight gap. Good results have been obtained where such gap is in therange of 0.001 to 0.250 inches. This insures that the wide bars 42remain intermeshed with one another except when upper roll 34 must swingupwardly to pass a slug of material, thus assuring a powerfulcompressing action against the already crimped stems of materials fromrolls 30 and 32. The resilient surface of rear rolls 34, 36 assists inapplying the appropriate compressive force to the crop stems when therolls are close together while allowing for manufacturing inaccuraciesduring formation of the long, helical bars 42.

Preferably, the front rolls 30, 32 rotate at essentially the same speedsas the rear rolls 34, 36, but somewhat faster than the gathering augers22 and 24. This produces a condition in which the conditioning mechanism28 tends to draw materials from augers 22, 24 such that there is littleor no tendency for crop materials to accumulate upstream from frontrolls 30, 32. Moreover, rear rolls 34 and 36 are positioned as close aspossible to front rolls 30, 32 without making actual contact therewith.This increases the reliability of the transfer of materials from frontrolls 30, 32 to rear rolls 34, 36.

To prepare the machine for conditioning operations, the operator mustpressurize the tension mechanism 80 to the desired level. Rear rolls 34,36 may be set at a higher or lower tension than front rolls 30, 32, asdesired by the operator. This is accomplished by first manipulatingswitch 154 such that an electrical circuit is completed through contact156, operating solenoid valve 148 to enable pump 144 to charge thesystem. One or the other of the shut-off valves 168, 174 is opened atthis time while the other remains closed such that pressurized oilenters the opened line, such as tension line 162, to extend frontcylinders 72, 74 and bring the pressure level in that portion of thecircuit up to the desired level. Meter 170 may be used to determine whenthe desired pressure level has been reached, at which time valve 168 maybe closed to trap oil in tension cylinders 72 and 74 at the desiredlevel. Thereupon, valve 174 may be held open in the same manner tocharge the rear tension cylinders 76 and 78 until such time as thedesired pressure level is indicated by meter 176. Thereupon, valve 174is closed, trapping pressurized oil in the extended rear tensioncylinders 76, 78 at the selected level. Returning switch 154 to itsstandby position of FIG. 9 will then allow solenoid valve 148 to close.If, for any reason, it is necessary to reduce the pressure level ineither the front tension cylinders 72, 74 or the rear tension cylinders76, 78, it is only necessary to manipulate switch 154 to establish acircuit through contact 158, thereby actuating the solenoid valve 152 toopen a drain path to reservoir 142. By then opening the appropriateshut-off valve 168 or 174, the pressure level in that part of thecircuit can be lowered to the desired level and then the valve 168 or174 returned to its closed position to terminate further discharge.Returning switch 154 to its standby position of FIG. 9 correspondinglyallows solenoid valve 152 to reclose.

Charging of the tension cylinders 72, 74 and 76, 78 causes the rolls 30,32 and 34, 36 to come close together to the extent permitted by the stopstructures 82 and 96. In the event that the running gap between frontrolls 30, 32 needs to be changed, it is a simple matter to manipulateadjustment nuts 92 in the appropriate direction to either enlarge orreduce the running gap. Similarly, in the event that the running gapbetween rear rolls 34, 36 needs to be changed, it is a simple matter tomanipulate nuts 104 of stop structure 96 in the appropriate direction toeither enlarge or reduce the dimensions of the running gap.

As the machine moves through the field of standing crop, rotating reel20 bends, deflects and sweeps the standing materials into sickle 18which severs the materials from the ground and allows them to be sweptupwardly and rearwardly by reel 20 into engagement with thecenter-gathering augers 22 and 24. Augers 22 and 24 consolidate thematerials centrally while distributing them evenly across the full widthof opening 26, and then transfer such materials into the conditioningmechanism 28. The front rolls 30, 32 receive the crop flow from augers22, 24 and subject the stems of the crop flow to a crimping action asthe stems pass between the intermeshed ribs of rolls 30, 32. At the sametime, front rolls 30, 32 serve as feeders to propel the conditionedmaterials rearwardly into and through the gap between rear rolls 34, 36,which rolls grab the material and flatten the stems thereof as a resultof the intermeshing bars 42. Rear rolls 34, 36 project the fullyconditioned materials on rearwardly in a forceful stream that engagesthe forming shields 16 and is directed down to the ground in either awindrow or swath, depending upon the adjusted positions of shields 16.

The front rolls 30, 32 play an important role in that they not onlylightly condition the crop, but also aggressively feed such materialsinto and through the rear rolls 34, 36. As a result of the aggressivefeeding action provided by front rolls 30, 32, the squeeze pressure ortension supplied by rear rolls 34, 36 can, if desired, be higher thanmight otherwise be the case, resulting in a more effective flattening ofthe crop stems. Likewise, the gap between rear rolls 34, 36 can besmaller. Providing the rear rolls 34, 36 with a compressive surface suchas rubber or other material is helpful in assuring positive feed of thematerials through rolls 34, 36, while at the same time providing asufficient conditioning action. Having rolls 34, 36 configured withwide, shallow lugs or bars as illustrated is also conducive to improvedfeeding action. And by providing the hard, preferably metal front rolls30, 32 ahead of the softer rear rolls 34, 36, the rear rolls 34, 36 aremore protected from stones and other hard objects which can be repelledand diverted by the metal conditioning rolls.

The inventor(s) hereby state(s) his/their intent to rely on the Doctrineof Equivalents to determine and assess the reasonably fair scope ofhis/their invention as pertains to any apparatus not materiallydeparting from but outside the literal scope of the invention as set outin the following claims.

1. In a machine for conditioning crop materials, the improvementcomprising: a front pair of mutually oppositely rotatable,non-compressible surface rolls adapted to receive a stream of cropmaterials, condition the materials as they pass between the rolls, andfeed the materials rearwardly, each of said front rolls being providedwith a set of generally radially outwardly projecting; elongated ribsextending generally helically lengthwise of the roll, the ribs of onefront roll being adapted to intermesh with the ribs of the other frontroll; a rear pair of mutually oppositely rotatable, compressible surfacerolls disposed to receive crop materials from the front rolls andsubject the crop to a further conditioning action, each of said rearrolls being provided with a set of generally radially outwardlyprojecting, elongated bars extending generally helically lengthwise ofthe roll, the bars of one rear roll being adapted to intermesh with thebars of the other rear roll, the rolls of each pair of rolls beingrelatively movable toward and away from one another; and tensionmechanism operably coupled with the front and rear pairs of rolls in amanner to resist said relative movement of the rolls of each pair awayfrom one another, said tension mechanism including hydraulic cylindersconnected in a hydraulic circuit.
 2. In a machine as claimed in claim 1,said hydraulic circuit including valving operable when closed to trappressurized hydraulic fluid within the cylinders.
 3. In a machine asclaimed in claim 2, said valving being operable when opened to allowcharging of the hydraulic cylinders with pressurized hydraulic fluid toa selected pressure level or discharging of hydraulic fluid from thecylinders to a selected pressure level.
 4. In a machine as claimed inclaim 2, said hydraulic circuit further including a compressible gasaccumulator connected in flow communication with the hydraulic cylindersto provide a cushioning effect.
 5. In a machine as claimed in claim 1,the helical pattern of the ribs on the front rolls extending the fulllength of the front rolls, the helical pattern of the bars on the rearrolls extending the full length of the rear rolls.
 6. In a machine forconditioning crop materials, the improvement comprising: a front pair ofmutually oppositely rotatable, non-compressible surface rolls adapted toreceive a stream of crop materials, condition the materials as they passbetween the rolls, and feed the materials rearwardly, each of said frontrolls being provided with a set of generally radially outwardlyprojecting, elongated ribs extending generally helically lengthwise ofthe roll, the ribs of one front roll being adapted to intermesh with theribs of the other front roll; a rear pair of mutually oppositelyrotatable, compressible surface rolls disposed to receive crop materialsfrom the front rolls and subject the crop to a further conditioningaction, each of said rear rolls being provided with a set of generallyradially outwardly projecting, elongated bars extending generallyhelically lengthwise of the roll, the bars of one rear roll beingadapted to intermesh with the bars of the other rear roll, the rolls ofeach pair of rolls being relatively movable toward and away from oneanother; and tension mechanism operably coupled with the front and rearpairs of rolls in a manner to resist said relative movement of the rollsof each pair away from one another, said front and rear pairs of rollspresenting a pair of upper rolls and a pair of lower rolls, one of theupper rolls being fixed and the other upper roll being mounted forpivoting movement about the axis of rotation of the fixed upper roll,one of the lower rolls being fixed and the other lower roll beingmounted for pivoting movement about the axis of rotation of the fixedlower roll, the movable upper roll being pivotal toward and away fromthe fixed lower roll, and the movable lower roll being pivotal towardand away from the fixed upper roll.
 7. In a machine as claimed in claim6, said tension mechanism including a pair of hydraulic cylindersoperably coupled with respective ones of the movable rolls, each of saidhydraulic cylinders being connected in a hydraulic circuit that includesvalving operable when closed to trap pressurized hydraulic fluid withina corresponding cylinder, said valving being operable when open to allowcharging of the hydraulic cylinders with pressurized hydraulic fluid toa selected pressure level or discharging of hydraulic fluid from thecylinders to a selected pressure level, each of said cylinders havingits own valving operable independently of the valving for the othercylinder.
 8. In a machine as claimed in claim 7, each of said hydrauliccylinders having a compressible gas accumulator connected in fluid flowcommunication with the cylinder to provide a cushioning effect for thecylinder.
 9. In a machine as claimed in claim 6, the helical pattern ofthe ribs on the front rolls extending the full length of the frontrolls, the helical pattern of the bars on the rear rolls extending thefull length of the rear rolls.
 10. In a machine for conditioning cropmaterials, the improvement comprising: at least one pair of oppositelyrotatable rolls for acting upon a stream of crop materials passingbetween the rolls, said rolls being relatively movable toward and awayfrom one another; and hydraulic tension mechanism operably coupled withthe rolls without springs for supplying a tension force resistingmovement of the rolls away from one another, said tension mechanismincluding a hydraulic cylinder connected in a hydraulic circuit, saidhydraulic circuit including valving operable when closed to trappressurized hydraulic fluid within the cylinder, said valving beingoperable when opened to allow charging of the hydraulic cylinders withpressurized hydraulic fluid to a selected pressure level or dischargingof hydraulic fluid from the cylinder to a selected pressure level, saidhydraulic circuit further including a compressible gas accumulatorconnected in flow communication with the hydraulic cylinder to provide acushioning effect, further comprising a second pair of oppositelyrotatable rolls movable relatively toward and away from one another anddisposed to receive crop materials from the first-mentioned pair ofrolls for acting upon such materials as they pass between the secondpair of rolls, said tension mechanism being operably coupled with saidsecond pair of rolls for resisting movement of the second pair of rollsrelatively away from one another, said tension mechanism including asecond hydraulic cylinder coupled without springs with said second pairof rolls, said first-mentioned hydraulic cylinder and said secondhydraulic cylinder each having valving adapted to trap pressurized fluidin the cylinders, said valving being operable to permit fluid to betrapped in the first-mentioned cylinder at a different pressure levelthan fluid trapped in said second cylinder, said first-mentioned rollscomprising a pair of non-compressible surface rolls, each having a setof generally radially outwardly projecting ribs that extend generallyhelically along the length of the roll, said second rolls comprising apair of compressible surface rolls, each having a set of generallyradially outwardly projecting bars that extend generally helically alongthe length of the roll.
 11. In a machine as claimed in claim 10, thehelical pattern of the ribs on the front rolls extending the full lengthof the front rolls, the helical pattern of the bars on the rear rollsextending the full length of the rear rolls.
 12. A method ofconditioning crop materials comprising the steps of: presenting cropmaterials to a front pair of oppositely rotating, non-compressiblesurface rolls having intermeshing ribs that extend generally helicallylengthwise of the rolls; passing the crop materials between the frontrolls while the rolls are under tension to condition the materials;presenting the conditioned materials from the front rolls to a rear pairof oppositely rotating, compressible surface rolls immediately behindthe front rolls, said rear rolls having intermeshing bars that extendgenerally helically lengthwise of the rear rolls; and passing theconditioned crop materials between the rear rolls while the rear rollsare under tension to subject the conditioned materials to a furtherconditioning action, wherein the tension force is applied hydraulicallyto the front rolls and the rear rolls.
 13. A method of conditioning cropmaterials comprising the steps of: presenting crop materials to a frontpair of oppositely rotating, non-compressible surface rolls havingintermeshing ribs that extend generally helically lengthwise of therolls; passing the crop materials between the front rolls while therolls are under tension to condition the materials; presenting theconditioned materials from the front rolls to a rear pair of oppositelyrotating, compressible surface rolls immediately behind the front rolls,said rear rolls having intermeshing bars that extend generally helicallylengthwise of the rear rolls; and passing the conditioned crop materialsbetween the rear rolls while the rear rolls are under tension to subjectthe conditioned materials to a further conditioning action, furthercomprising the step of adjusting the tension on the front rollsindependently of the tension on the rear rolls.
 14. A method ofconditioning crop materials comprising the steps of: presenting cropmaterials to a front pair of oppositely rotating, non-compressiblesurface rolls having intermeshing ribs that extend generally helicallylengthwise of the rolls; passing the crop materials between the frontrolls while the rolls are under tension to condition the materials;presenting the conditioned materials from the front rolls to a rear pairof oppositely rotating, compressible surface rolls immediately behindthe front rolls, said rear rolls having intermeshing bars that extendgenerally helically lengthwise of the rear rolls; and passing theconditioned crop materials between the rear rolls while the rear rollsare under tension to subject the conditioned materials to a furtherconditioning action, further comprising the step of adjusting spacingbetween the front rolls independently of adjusting spacing between therear rolls.
 15. In a method as claimed in claim 12, the helical patternof the ribs on the front rolls extending the full length of the frontrolls, the helical pattern of the bars on the rear rolls extending thefull length of the rear rolls.
 16. In a method as claimed in claim 13,the helical pattern of the ribs on the front rolls extending the fulllength of the front rolls, the helical pattern of the bars on the rearrolls extending the full length of the rear rolls.
 17. In a method asclaimed in claim 14, the helical pattern of the ribs on the front rollsextending the full length of the front rolls, the helical pattern of thebars on the rear rolls extending the full length of the rear rolls.